ch 11.docx

CH 11: THE BLOOD
 8% of total body weight is from blood (5L female; 5.5L in males)
 Consist of plasma and either erythrocytes, leukocytes or platelets
o RBC’s and WBC’s = whole cells; platelets are cell fragments
 Hematocrit aka packed cell volume – represents the percentage of
erythrocytes in total blood volume (of ones body), which is around 45% in
humans; WBC’s are only around 1% of total blood volume
PLASMA (is a liquid which has 90% water)
 The plasma H O2is used to allow materials to enter the blood, and hold heat
(can distribute heat to tissue, while keeping the blood heat at a constant
temp) – when the blood travels near skin, heat not needed is eliminated into
the environment
 Plasma holds organic and inorganic substances
o Inorganic: electrolytes (Na and Cl being most common); also used to
excite the membrane, distribute H O2to ECF and cells (osmosis), pH
buffer
o Organic: plasma proteins, nutrients, waste, dissolved gases (O /2O ) 2
and hormones
 Plasma proteins: normally stay in the plasma
o Are dispersed as a colloid; also are the largest molecules in plasma so
they don’t escape the capillaries into the interstitial fluid (this creates
an osmotic pressure), so plasma cannot excessively be lost from the
capillaries as well
o Responsible for buffer changes in pH
o There are 3 groups (see c.kit pg 211)
ERYTHROCYTES
 Mainly used for transporting O 2nd a lesser extent of CO 2nd H ions
 The biconcave disk shape of the RBC is used to create a larger surface area
for diffusion of 2 and bc of its thinness, it allow2 O to diffuse rapidly bw the
exterior and interior of the cell
 The membrane is also able to deform so they can squeeze through the
capillaries without rupturing
 Hemoglobin – read c.kit pg 215-218
Bone Marrow
 RBC’s cant divide, repair, grow or renew enzyme supply (since they lack RNA
and DNA needed to create proteins) so they only survive around 120 days
 Cells become more fragile as they continue to squeeze through capillaries
and become prone to rupture – they normally die in the spleen where there
are very narrow capillaries that the cells cant squeeze through
o Spleen removes the old RBC’s, is a reservoir site for platelets and also
contains lymphocytes
 Erythropoiesis: generation of new RBC’s in the bone marrow o Bone marrow: soft, highly cellular tissue in the internal cavities of
bones
 Read about erythropoiesis on page 220 of c.kit
 Read steps of RBC production on page 221
 Note reduced O t2at’s being delivered to the kidneys is what stimulates the
erythropoietin (EPO) to be stimulated into the blood
Lower O 2 kidneys create EPO  EPO stimulate erythropoiesis by red marrow
 This allows the O2carrying capacity in the blood to remain constant
 The time required to replace all of the lost RBC’s depends on how many are
needed to return to normal levels i.e. when you donate blood the supply is
replenished faster than when you loose a whole lot of blood
 If the demand for RBC’s is really high (like following a hemorrhage)
reticulocytes may be released
o These are immature RBC’s that still contain organelles – when there
are many it means that there is a high rate of erythropoietic activity
Anemia
 Read about on page 222 c.kit
 Hemolysis: rupture of RBC’s (can lead to hemolytic anemia)
o Happens bc normal cells are induced to rupture by external factors,
invasion of RBCs by malaria or bc the cells are defective like in sickle
cell disease (read about on page 224-225)
Polycythemia
 Viscosity of blood is based on the number of RBCs – increase RBC leads to
increase drag of RBC’s and the vessel walls
 Measure RBC by using hematocrit – if hematocrit is 42%, then the persons
blood volume has 42% cells (mainly RBC’s) and the remaining amount (38%)
is plasma – this is NORMAL levels
 Increased amounts of hematocrit – harder for the heart to pump blood,
therefore harder for tissue to get 2
 Polycythemia – read about on page 222 and 224
LEUKOCYTES (WBCs) – body’s immune defense system
 Immunity: body’s ability to resist/eliminate potentially harmful foreign
materials or abnormal cells
 Read about immune system functions on page 229 c.kit
 WBC’s use a “seek out and attack” strategy – can only carry their function
when they go to sites of invasion or tissue damage (the main reason for them
to be in the blood is so they can transport rapidly)
